1. Field of the Invention
The invention relates generally to solid state sensors, and more specifically to such sensors that can be implemented on a single integrated circuit chip, and respond to luminosity information in a first spectral band such as red, green, blue optical wavelengths (which shall be understood to include black and white) to acquire an red-green-blue (RGB) image, and respond to wavelengths in a second spectral band, preferably near-infrared (NIR), to acquire Z data.
2. Description of Related Art
Luminosity-based sensors are known in the art. Such sensors are commonly implemented using CMOS techniques and include an array of pixel detectors responsive to wavelengths in a first spectral band, e.g. red, green, blue wavelengths (RGB sensors) or simply gray scale wavelengths (black and white or BW sensors). The array can be fabricated upon an integrated circuit (IC) substrate upon which may be fabricated analog-to-digital conversion circuitry and signal processing circuitry. While such sensors can provide a color (RGB) or gray scale (BW) image, they provide no useful depth information.
FIG. 1 depicts an exemplary application of a conventional RGB or BW sensor. Suppose that it is desired to use a camera system to intelligently recognize objects within a field of view. In some applications the camera system might be provided in or on a motor vehicle to scan the road ahead for target objects that might be endangered by the motor vehicle, pedestrians perhaps. An exemplary camera system includes a lens 20 that receives red, green, and blue components of visible light energy 30 reflected from a target object 40 a distance Z away from the camera system. Associated with the camera system is a prior art RGB sensor 50 that outputs a signal responsive to the incoming RGB light components. In this particular application, a sensor circuit 60 receives an output signal from sensor 50 and attempts to identify the target object 40 in terms of hazard potential. If desired, output from the camera system may include an image 70 electronically generated, for example on a flat screen monitor screen (or in some applications printed on media such as paper). In a hazard warning application image 70 might be displayed within a red circle to designate an immediate hazard to be avoided, and sensor circuit 60 may also cause audible warnings to be sounded.
Although resolution of RGB sensor 50 may be adequate to display target object 40, rapid identification of the nature and size of the target would be improved if Z data, usually acquired from IR wavelengths, could also be used. Such information, if available, could also be used to provide a measure of the actual size of the target object.
It is also known in the art to fabricate range-finding or three-dimensional sensors. For example, U.S. Pat. No. 6,515,740 to Bamji et al. (issued Feb. 4, 2003) discloses a sensor system that provides depth information (Z-distance between the sensor and a target object) at each pixel detector in the sensor array. Range-finding detectors according to the '470 patent use a modulated light source operating at preferably near infrared wavelength (perhaps 800 nm). As used herein, let it be understood that the term “RGB” may include “gray scale” or “BW” wavelengths, and that the term “IR” may include “near IR” (NIR) wavelengths.
In many applications it can be important to simultaneously acquire from a single field of view or bore sight both data in a first spectral band, typically RGB data (used to provide an RGB image) and Z data (preferably acquired at in a second spectral band, typically IR wavelengths). But this goal is difficult to attain in practice because pixel detectors used to capture Z-data at IR wavelengths are commonly much larger in area than pixel detectors responsive to RGB wavelengths. For example the cross-sectional area of an exemplary Z-data pixel detector might be 50 μm×50 μm, compared to an exemplary area of perhaps 5 μm×5 μm for an RGB pixel detector. If a single array were fabricated to simultaneously use RGB pixel detectors and Z pixel detectors, the presence of the large sized Z pixel detectors in a high density array of much smaller sized RGB pixel detectors would cause large image artifacts that could degrade the quality of a resultant RGB image. Further, pixel detectors responsive to Z data often require high quality (preferably IR wavelength) bandpass filtering. In practice, CMOS fabrication does not presently implement such bandpass filtering for the Z pixels, especially with desired narrow band characteristics that may be on the order of 50 nm or less.
Thus there is a need for a sensor that includes pixel detectors responsive to wavelengths in a first spectral band, such as RGB wavelengths, and that also includes pixel detectors responsive to preferably Z data in a second spectral band, preferably NIR wavelengths. Preferably such sensor array should be implementable on a single IC substrate.
The present invention provides such a sensor.